1. Field of the Invention
Embodiments of the present invention relate to a multi-layer electrode and a compound semiconductor light emitting device comprising the same, and more particularly, to a multi-layer electrode having low contact resistance, improved electrical conductivity, and especially, high light transmittance and a compound semiconductor light emitting device comprising the same.
2. Description of the Related Art
Compound semiconductor light emitting devices, for example, semiconductor laser diodes such as light emitting diodes (LEDs) and laser diodes (LDs), convert electric signals into optical signals using the characteristics of compound semiconductors. Laser beams of the compound semiconductor light emitting devices have been applied practically in the fields of optical communications, multiple communications, and space communications. Semiconductor lasers are widely used as light sources for data transmission or data recording and reading in the field of optical communications and such apparatuses as compact disk players (CDPs) or digital versatile disk players (DVDPs).
A compound semiconductor light emitting device can be categorized into a top-emitting light emitting diode (TLED) and a flip-chip light emitting diode (FCLED) according to the emission direction of light.
In the case of the FCLED, light emitted from an active layer is reflected by a reflective electrode formed on a p-type compound semiconductor layer, and the reflected light passes through a substrate.
The TLED emits light through a p-type electrode, which forms an ohmic contact with a p-type compound semiconductor layer. The p-type electrode may include a Ni layer and an Au layer, which are sequentially stacked on a p-type compound semiconductor layer. However, since the p-type electrode, formed of the Ni layer and the Au layer, is translucent, the TLED including the p-type electrode has low optical efficiency and low brightness.
To solve these problems, research on materials and structures for an electrode having low contact resistance and high light transmittance has been conducted.